Invasive Species Management

Invasive plants have been silently consuming the Town of Kittery — out-competing native species, destroying bird and animal habitat, diminishing native biodiversity, and degrading our natural landscape. Left unchecked, they will forever change the ecology and character of our small community.

Fortunately, it’s easy to make a difference. Here some of the most common offenders to help homeowners identify and remove these undesirables from their own property.

Barberry (berberis thunbergii)Berberis thunbergii is shade tolerant, and forms dense stands in a variety of habitats ranging from closed canopy forests, to woodlands, wetlands, pastures, meadows and wasteland. It is readily dispersed by birds, which can bring the seeds many meters away from the parent plants.

Bittersweet poses a serious threat to other species and entire habitats due to its aggressive habit of twining around and growing over other vegetation. This plant has a high reproductive rate, long-range dispersal mechanisms, and the ability to root-sucker. The vines can strangle tree and shrub stems. All types of plants—even entire plant communities— can be over-topped and shaded out by the vine’s rapid growth. Virtually pure stands of this vine are sometimes found in affected areas, and it’s recently been discovered colonizing sand dunes in Connecticut and Rhode Island.

Perennial, deciduous shrub, broadly branched, up to ~15′ tall, forms dense thickets. Some stems have corky “wings.” Small plants and seedlings may be pulled up by the roots when soil is moist; larger plants can be cut, but re-sprouting will occur.* Persistent cutting or mowing multiple times during the growing season over several years may kill the plant, but diligence is required. Mowing can prevent seedlings from establishing. Herbicides† are effective as foliar applications (2-3% glyphosate solution) or cut-stump applications (20-25% glyphosate or triclopyr solution applied immediately after cutting).

Also called golden-thread or love vine; A climbing, parasitic, yellow or orange vine that produces small, dense clusters of tiny white, bell-shaped flowers; Leaves are reduced to a few very tiny scales; Vines tightly wrap around the stems of cranberry (and other) plants and absorb their liquid contents through tiny suckers; it needs other plants to serve as a host before it can attach to cranberry vines. [annual]

Control:Pull and destroy plants infested by the dodder prior to the dodder setting its seeds because the seeds are so numerous and can spread so easily – It is best to pull the dodder-infected upright(s) out of the bed, or else the dodder may sprout again from inside the upright(s). In addition, it is advised to “flag” the area(s) where the dodder is found in order to monitor for additional dodder plants from day-to-day. Seeds may spread via wind or floodwaters.

Leaves: Lower are toothed and kidney shaped, ¾-4″ long, and form a basal rosette that overwinters. Upper are toothed and triangular, alternate along flowering stem. Crushed leaves smell like garlic. Flowers/Seeds: Abundant ¼” white, 4-petaled flowers, produced form April-June, in its second season. Skinny seed capsules 1-2.5″ split open in mid-late summer releasing tiny black seeds, several hundred per plant on average. Plants die after seed set. Root: Tap root is white and is often S-shaped near the stem.

Leaves are simple, 1.5-3.5″ long, oval and opposite. Occasionally, leaves low on the vine may have rounded lobes. Leaves appear early and stay on plant late, providing photosynthetic advantage. Flowers/seeds: Fragrant tubular flowers appear May –June and are 1- 1.5″ long, creamy white, with two reflexed lips and long stamens. They occur in pairs between leaves and form black berries in fall.

Habitat: Disturbed areas such as roadsides, field edges, and floodplains. Windthrows, logging, and insect outbreaks provide entry into woodlands.

Knotweed

Robust, very tall (to 10′) perennial herb growing in dense stands.

Leaves: Simple, alternate, entire, flat at base and abruptly tapering to pointed tip, ~6″ long and 3-4″ wide. Flowers: Small, white, in small spikes along stems, late summer in Maine (late July or August). Fruits: Often sterile, but fruits when present have thin “wings” to enable wind dispersal. Stem: Round, hollow, with swollen nodes where leaves meet the stem. Dead, brown-red stalks persist through winter.